IEEE - 49239

Planar Yagi-Uda Antenna with

Mirrored Ground Plane for WLAN
Ravi K Tanti #1, Saurabh Warathe#2, Dr. N. Anveshkumar *3
1,2
Electronics Department, RCOEM
Nagpur, Maharashtra, India
1
ravitanti5@gmail.com
2
saurabhwarathe@gmail.com
3
Electronics and Communication Department, VIT Bhopal University, India
3
nellaanvesh@gmail.com

Abstract— The purpose of this research paper is to To develop a highly efficient directional antenna the
propose a planar compact Yagi-Uda antenna for WLAN Yagi-Uda antenna is chosen. The Yagi–Uda antennas are
2.4GHz band applications. This paper also discusses known for their high directivities. In Yagi–Uda antennas a
techniques to enhance the gain and directivity of the linear array of metal rods worked as feed, reflector, and
antenna by introducing an inverted mirror J structure on directors [2, 3]. The emanating electromagnetic wave from
the ground plane and directors on the top plane. The
the feed element induces a current in other passive elements
proposed antenna is designed and fabricated on an FR-4
substrate of dimensions 55mm×48mm×1.6mm. This of the antenna array, which results in phase-coherent
antenna operates in the WLAN 2.4GHz band with a center emissions from all the elements in the array [4]. Its
frequency of 2.45GHz having a peak gain of 4.34dBi, directivity and high gain make Yagi-Uda suitable for our
radiation efficiency as 87.56%, and a reflection coefficient applications. Yagi- Uda consists of huge ground plates that
of -26.81dB. In this paper, a conventional Yagi-Uda are employed as reflectors. Hence, these antennas typically
antenna is presented at first and then through the have large sizes and which hampers the antenna efficiency
methodical optimization process, a modified design with as well as array composing. The size and difficulties can be
enhanced gain and directivity characteristics is proposed. deeply condensed if the feeding structure of the antenna can
Lastly, the antenna is fabricated and then measured. The
be designed excluding the large ground plate [5].
simulation results are validated after measurement.
The planar Yagi-Uda antennas have attracted much
Keywords— Co-planar stripline, finite element attention due to their broad bandwidth, high gain, low cost,
method, microstrip antenna, wireless local area network, and ease of fabrication [6]. Several different feeding
worldwide interoperability for microwave access, Yagi- structures have been studied in Yagi-Uda antennas, such as
Uda antenna. a coplanar waveguide (CPW) feed with a coplanar
waveguide-coplanar stripline (CPW-CPS) transition [7],
I. INTRODUCTION microstrip line feed with a microstrip-coplanar stripline
Wireless communication and data transfer have (MS-CPS) transition [8], and with a microstrip line feed
become an integral part of many people's daily life. without any transition structure [9]. The Yagi-Uda antennas
Devices like phones, laptops, smartwatch, and other can be easily integrated with today’s wireless
devices use wireless data transfer technologies such as communication systems because they show both small and
WLAN and Wi-MAX to connect to the internet [1]. broadband properties. In 1998, a printed quasi-Yagi-Uda
Wireless technology can also be used in military and antenna was projected by Qian et. al [10].
medical body-worn applications. Recently, in a health The purpose of the research work is to develop new
care monitoring system, these biomedical sensors and methodologies to enhance the performance of Yagi-Uda
implants within the human body have sought great antennas by increasing gain and directivity. In this research
attention. As with the growing population and age, the paper, the proposed antennas are designed using HFSS
demand for health care has been increased. These software. It is a finite element method (FEM) based on the
wearable monitoring have the capability to monitor EM structure simulator. FR-4 material is used as a dielectric
medical data in a real-time form, which it can also substrate used in the antennas, with a dielectric constant of
predict the time of stroke and other diseases. These 4.4 and a loss tangent of 0.019. Initially, a conventional
monitoring devices which use WLAN and Wi-MAX Yagi-Uda antenna was designed and then by studying its
technologies require an antenna. The crucial bandwidth various parameters, the elements affecting gain and
required for this is the 2.4GHz band (2.4 GHz – 2.5 directivity were identified.
GHz) as per IEEE 802.11 standard.

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 IEEE - 49239

II. LITERATURE SURVEY The simulated return loss performance of the proposed
antenna is shown in Fig. 2.
The frequency at which the antenna operates has a
significant impact on the size and gain of an antenna.
According to a literature survey [11], a Yagi-Uda
antenna having a center frequency of 2.45GHz with
dimensions 66mm×38mm has a peak gain of 3.67dBi.
In another research work, a quasi-Yagi antenna was
designed [12]. The dimensions of the antenna were
found to be 50mm×50mm×1.58mm and have a peak
gain of 5.5dBi. A similar quasi-Yagi antenna operating
from 2.3GHz to 3.8GHz was proposed with dimensions
70mm×54mm and has a peak gain of 5dBi [13].
Similarly, a planar inductively coupled bow-tie slot
antenna was designed with an operating frequency of
2.45GHz [14]. This antenna is having dimensions Fig. 2. Simulated reflection coefficient curve for planar microstrip line
80mm×49.5mm×1.5mm and has a peak gain of 4.2dBi antenna.
[14]. The above-discussed antennas from different From Fig. 2 it is clear that the antenna has a center
works of literature give an insight into the different frequency of 2.45GHz with reflection coefficient dB(S(1,1))
methodologies to design a Yagi-Uda antenna for of -27.81dB. The exhibited simulation result of peak gain
WLAN applications. The motivation for our proposed for the proposed antenna is shown in Fig. 3.
research work is to suggest a different technique to
enhance the peak gain with a reduced dimension.

III. PLANAR MICROSTRIP LINE ANTENNA

A planar microstrip line antenna is discussed in this

section, which is operating at a frequency of 2.45GHz.
The antenna has an inverted J structure, which acts as
an active region and a partial ground on the other side.
After the parametric analysis, the substrate dimensions
were minimized, which gives a bandwidth ranging from
2.29GHz to 2.6GHz with VSWR ≤ 2 and a center
frequency at 2.45GHz. The resulting smallest possible Fig. 3. The radiation pattern of the proposed antenna at 2.45GHz.
dimension was found to be 25mm×48mm as shown in
From Fig. 3 it was found that the radiation pattern is
Fig. 1.
omnidirectional and the antenna has a peak gain of 0.53dBi
with a radiation efficiency of 93.29%. This is very less
when microstrip line antennas were considered hence an
improved modified antenna was suggested.

IV. PROPOSED ANTENNA WITH DIRECTIVITY AND GAIN

ENHANCEMENT
In the proposed antenna discussed in section III, the gain
is decreased due to omnidirectional radiation. To overcome
this problem a modified antenna has been introduced. The
(a)
modified antenna consists of directors, which are shorter
than the radiating element of the antenna. The directors are
not directly connected to the active element but pick up
power from the radiating element and re-radiate it. It affects
the properties of the whole Yagi antenna, causing the power
to be focused in one particular direction. Factors like length
and spacing between directors affect the phase and
amplitude of the current induced in the parasitic elements. A
(b) passive element becomes capacitive when it is shorter than
Fig. 1. Planar microstrip line antenna. (a). Top view. (b). Bottom the active element and it becomes inductive when it is larger
view. than the active element. In the backside of the antenna as

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shown in Fig. 4 the ground plane acts as a reflector further simulated and gain, radiation pattern was observed
which reflects the wave in the directions of directors as shown in Fig. 6.
results in the improved directivity. The modified
antenna consisting of five directors is shown in Fig. 4.

Fig. 6. The radiation pattern of the antenna at 2.45GHz.

From Fig. 6 it was found that the gain, as well as
directivity of the modified antenna, has been increased. The
(a) (b)
gain was increased from 0.53dBi to 2.42dBi with a radiation
Fig. 4. Planar Yagi-Uda antenna. (a). Top view. (b). Bottom view.
efficiency of 92%. In our next antenna, to further increase
The directors are placed in such a way to increase the the gain and directivity a mirrored inverted J was introduced
directivity and gain of the antenna. The modified in a non-active plane as shown in Fig. 7.
antenna was fabricated on the FR4 substrate of
dimensions 55mm×48mm and the width of all passive
elements were kept constant to 3mm. The length of
directors and the spacing is given in Table I was
adjusted to achieve a great directivity and gain.
TABLE I
DESIGN PARAMETERS OF MODIFIED ANTENNA
S. No. Element Size in mm
1 a 32
2 b 30
3 c 28
4 d 26
5 v 4
6 w 4 Fig. 7. Mirrored ground plane to the Yagi-Uda antenna.
7 x 4.25 The simulated return loss performance of the proposed
8 y 3.75 antenna is shown in Fig. 8.
The simulated return loss performance of the
proposed antenna is shown in Fig. 5.

Fig. 8. Simulated reflection coefficient curve for the Yagi-Uda antenna

with mirrored inverted J.
Fig. 5. Simulated reflection coefficient curve for Yagi-Uda antenna. From Fig. 8 it is clear that the antenna has a center
From Fig. 5 it is clear that the antenna has a center frequency of 2.45GHz with reflection coefficient dB(S(1,1))
frequency of 2.45GHz with reflection coefficient of -26.81dB. The modified antenna was further simulated
dB(S(1,1)) of -23.38dB. The modified antenna was and gain, radiation pattern was observed as shown in Fig. 9.

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From Table II, it is found that the peak gain has

drastically increased from 0.5dBi to 4.34dBi with a slight
variation in dB(S(1,1)). The antenna was fabricated as
shown in Fig. 11 and its various parameters were tested on a
vector network analyzer (VNA).

Fig. 9. The radiation pattern of the proposed antenna at 2.45GHz.

From Fig. 9 it was found that the peak gain of
antenna has been approximately doubled to 4.34dBi
with a radiation efficiency of 87.56% and its directivity
has also been increased. The 2D radiation patterns of
the three antennas are shown in Fig. 10. (a) (b)
Fig. 11. Fabricated proposed antenna. (a). Top View. (b). Back View.
The comparison between the simulated and measured
results is shown in Fig. 12.

Fig. 12. Comparison of simulation and measurement results.

From Fig. 12 it can be noted that a good agreement is
found between the simulation and measurement. A
comparison of proposed work with existing work is shown
in Table III.
TABLE III
Fig. 10. 2D radiation patterns at 2.45GHz.
COMPARISON OF PROPOSED WORK WITH EXISTING WORK
From Fig. 10 it can be noted that the gain is increased
with the technique of inverted mirror J structure on the Ref. Dimensions Operating Peak Gain
ground plane. The gain and effect of bandwidth were (mm×mm) Frequency (GHz) (dBi)
further analyzed for the above three antennas as shown [11] 66×38 2.45 3.67
in Table II. [12] 50×50 2.45 5.5
TABLE II [13] 70×54 2.45 5
SIMULATION RESULTS OF PARAMETERS [14] 80×49.5 2.45 4.2
Proposed 55x48 2.45 4.34
Sr. Type of Peak Gain Bandwidth dB(S(1,1)) at
antenna
No. antenna (dBi) (GHz) 2.45GHz
From the literature survey in Table III, it was found that
Microstrip
1
line antenna
0.53 0.3 -27.81dB the existing antennas have greater dimensions and peak
Yagi-Uda gains lower than our proposed antenna [11-14]. From the
2 2.42 0.27 -23.38dB proposed research work it was found that the microstrip line
antenna
Proposed antenna has slightly higher dB(S(1,1)) than proposed
3 4.34 0.2 -26.81dB
antenna antenna but lesser peak gain and directivity. The dB(S(1,1))

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 IEEE - 49239

of the proposed antenna was found to be -26.816dB and [10] Qian, Yongxi, William R. Deal, Noriaki Kaneda, and Tatsuo Itoh,
―Microstrip-fed quasi-Yagi antenna with broadband characteristics‖,
has a bandwidth ranging from 2.34GHz to 2.54GHz
Electronics Letters, Vol. 34, No. 23, pp. 2194-2196, 1998.
with VSWR ≤ 2 and a center frequency at 2.45GHz.
[11] Azizi, Syafiq Noor, Nornikman Hasan, and Mohamad Hafize Ramli,
―Design and Analysis of Yagi-Uda Antenna for WLAN
V. CONCLUSION Applications‖, Journal of Telecommunication, Electronic and
Computer Engineering (JTEC), Vol. 9, No. 1-3, pp.109-112, 2017.
In this research work, initially, an antenna with a [12] Farran, Mohamad, Daniele Modotto, Stefano Boscolo, Andrea
microstrip line was presented. It has a center frequency Locatelli, Antonio-D. Capobianco, Michele Midrio, and Vittorio
of 2.45GHz and a peak gain of 0.53dBi. Thereafter, to Ferrari, ―Microstrip-fed quasi-Yagi antennas for WLAN
improve its gain and directivity, five directors were applications‖, In 44th European Microwave Conference, pp. 1687-
1690, 2014.
introduced in decreasing length order, which
significantly improved antenna performance. The peak [13] Floc’h, Jean-Marie, and Ahmad El Sayed Ahmad, ―Broadband
quasi-Yagi antenna for Wi-Fi and Wi-Max applications‖ in Wireless
gain value of antenna with directors was found 2.42dBi Engineering and Technology, Vol. 4, No. 2, pp. 87-91, 2013.
with bandwidth, dB(S(1,1)) of 0.27GHz, -23.38dB, [14] Shams, K. M. Z., M. Ali, and H-S. Hwang, ―A planar inductively
respectively. To further improve its performance a coupled bow-tie slot antenna for WLAN application‖, Journal of
mirrored inverted J structure was added in the backside Electromagnetic Waves and Applications, Vol. 20, No. 7, pp. 861-
of the antenna. The peak gain was found to be 4.34dBi 871, 2006.
with a bandwidth of 0.2GHz and dB(S(1,1)) of -
26.81dB. After studying the comparative performance
of these antennas, it was found that the peak gain has
drastically increased with a reduction in bandwidth. At
last, the proposed Yagi-Uda antenna was fabricated and
verified to validate the simulated result. This antenna
has a variety of applications, such as PCS, UMTS,
WLAN, WiMAX, and health care monitoring systems.

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